Picc line and PE

I have a question regarding Picc lines and something that happened to me today at work. I am new to nursing and I am rather upset with this; I had been given a pt load that I was not at all familiar with at start of the day and one had a Picc line that was getting one dose, then the mini pump was to be shut off, disconnected; line flushed with saline. Fine; I disconnected it, but stupidly put the 'blue connector' back onto the cap end. Why i'll never know. then I had my pt assigment changed around 10 am. So, later around 3 pm my co-worker says she just about 'had a heart attack' on discovering the blue connector on the cap; this means there is an opening into the piic line; my question being; could he really potentially get an PE? or infection? I was told so by her, but wonder if this is true. I am rather discouraged and feeling down. Any feedback and encouragement welcomed. I am an older nurse coming back to nursing after doing the refresher course at a time when cutbacks are going on. I am trying to swing it and never really worked much in nursing to begin with; everything is terribly new to me. Including this new 'blue connector' .. thanks.